


I'll meet you at the old mouse hole

by Pi (Rhea)



Category: Rivers of London - Ben Aaronovitch
Genre: Dubious Consent, Dubious Consentacles, Inspired by a fic, M/M, No Spoilers, Not Britpicked, Not my original non-human character, PWP, Plot What Plot/Porn Without Plot, Tentacles
Language: English
Status: Completed
Published: 2017-03-27
Updated: 2017-03-27
Packaged: 2018-10-11 19:44:45
Rating: Explicit
Warnings: Creator Chose Not To Use Archive Warnings
Chapters: 1
Words: 3,955
Publisher: archiveofourown.org
Story URL: https://archiveofourown.org/works/10472748
Author URL: https://archiveofourown.org/users/Rhea/pseuds/Pi
Summary: A short history of Nightingale's relationship to the demon in the basement, and the start of something new.





	

**Author's Note:**

  * Inspired by [That What Brought Him Back](https://archiveofourown.org/works/1944330) by [Linpatootie](https://archiveofourown.org/users/Linpatootie/pseuds/Linpatootie). 



> Asmodai is a creation of Linpatootie in their fic [That What Brought Him Back](http://archiveofourown.org/works/1944330?view_adult=true#work_endnotes). This fic takes place in the universe of That What Brought Him Back, I don't think it's necessary to read that first but it's a great fic that this fic aspires to be as much fun as, so you should go read it ^_^

Thomas Nightingale only vaguely remembers the first time he was told to stay away from that particular door in the Folly. Thomas was a bit of a late bloomer, so unlike some of the other Folly residents he hadn’t felt it’s pull so keenly then. There hadn’t been any accompanying explanation to answer why the door was forbidden, but even with all he’d learned of magic already he might not have believed a demonic horror, an intelligent power that could pierce through thoughts and discern the desires of it’s prey, a many limbed creature that fed on sexual urges was truly held captive behind the complexly warded door.

Since Thomas Nightingale first actually encountered the demon Asmodai, the nature of their relationship, and the visions it’s shown him have changed over time. He was always curious as to how long the creature had dwelt beneath the Folly, trapped away from the outer world, but sealed rather poorly from generations of Folly residents. With all it’s been fed, however closely guarded, over the years, it’s pull has stayed strong and constant since the time Thomas began to actually notice it. Thomas remembers one memorable lecture, once he’d already experienced the hazards of trying the door, reprimanding new magicians to the Folly to stay away from it. All the threats were too vague to be truly intimidating, but Thomas now at least understood why no one wanted to explain the details behind the danger. The door practically proved diagnostic for selecting levels of magical aptitude and potential. Those who could open the door despite it’s spells and wards, and those who were simply found plastered to it’s metal surface on night patrol. Thomas had witnessed at least two practitioners shifted in focus of their work after such a scene. 

 

Thomas of course, had been able to open the door on the first try. Truly he’d been drawn as much by the sense of tradition around the act and the dichotomy between students who had tried to door and those who hadn’t, as by any personal inclination. Afterward he’d returned with restrained regularity, viewing it as another magical practice challenge. Secretly Thomas figured he was one of the most proficient in resisting the doors charms, experiences with the demon left a certain addled expression on the participants face, a mussiness that couldn’t be easily covered over. Partially his reticence was an intense distaste for the possibility of being caught out, as so many others had, and partially it was his own careful resistance to compulsion combined with his intense, single-minded focus on his work. In those days, whenever Thomas capitulated to the demon, it played through images of his fellow practitioners, and distressingly, once or twice, one of his professors from school. As pleasurable pastimes went, it was well enough, and certainly Thomas believed it had kept him from perhaps announcing himself to a particular other student. In later years Thomas was never sure whether to be grateful for his own self-restraint. He came to view the door and the images provided by the demon beyond with the regret of potential missed opportunities soured by the guilt of his own continuing age when the bodies of all his fellows were cold in the ground. 

 

Before that carnage, but after the moment when Thomas might have betrayed himself had he been less cautious with his feelings, Thomas had left the Folly and done his work across the globe, contributing to a safer English Empire. Some days it was hard to know what good had come of his actions. In each instance there may have been lives saved, and as the long arm of the Folly Thomas encountered a wider and fuller world of magic than many of his peers had imagined. With the same dedication of his schooling Thomas applied himself to learn the world. In doing so he assumed whatever tenuous connection still wavered back between himself and the metal basement door had been broken. Then, in the wake of the death and horror that had steeped in the bloody patches at the elbows of his coat, Nightingale had returned to the Folly. 

 

The first few weeks his mind played tricks with the echo of voices around him. Nightingale appropriated one of the larger rooms and moved himself into his own particular corner of the place, warding himself in as tightly as Asmodai behind the metal door, floors away. More and more alone Thomas continued on as he had been. He thought perhaps now it was harder to resist the demon, whether it was the lack of others around to offer their desires up to it, or Nightingale’s own abstracted longing for company. There were days when just the idea of a conversation was enough to draw him to the door’s metal surface and wearily Thomas could rest his head and just talk. He didn’t need to open the door. There just wasn’t enough of him left to contemplate anything further, and later the growing fear of what Asmodai might show him if he slipped behind the door stayed his hand. As the years passed, Nightingale wondered what might come of Asmodai when his own time had passed. If they were to sell the Folly in the wake of his death, what would be done about the demon, or for that fact, Molly? Her strange and familiar presence kept the place from falling down around his ears. The silver was shined and the floors gleamed in the lamplight. Everything but Thomas’ list of names was kept in its pristine original states. Sometimes Thomas wished he could convey how greatly this made the house feel like a mausoleum. A perfected museum to the life of the last magicians with Thomas himself a living specimen buried in the library. 

 

As the years passed and the trees around the property grew or fell, the lines around Nightingale’s eyes began to smooth. The brown seeped back into his hair. He left the Folly more and more often, to assist with police investigations or simply to marvel at the London that had grown up around him in his absence. He found himself recounting tales of the outside to Asmodai, drawn more easily behind the door with the return of his own vigor. As if perhaps understanding the concern behind his abstinence, the demon projected no faces before him and simply wore it’s own. In a strange way, this heartened Thomas, an edge of friendship to their carnal activity. He wondered if Asmodai had ever known someone this way before, after all there had been years and years of wizards before Nightingale. But then Thomas’ life began to change. 

 

First Peter and then Leslie joined the house, and with them a procession of visitors and voices bouncing up and down the corridors. Nightingale was extremely clear, as his predecessors had been, about the danger of the door. Leslie at least knew how to obey orders and was proud of her self-control, Peter on the other hand, in this as in most things, was a disaster waiting to happen. It wasn’t just that Peter had a unique propensity to explode physical objects around himself, nor his inquiring mind and keen interest in understanding the hows of any system, including magic. That he had to be so perceptive of others, generous and open in a way Nightingale had found that few coppers retained, and that he was fit to a standard that a much younger Thomas would have had to hastily turn his eyes from helped matters not a whit.  Thomas supposes then that he shouldn’t be surprised when his next visit to Asmodai takes a distressingly unexpected turn. 

 _Oh, who is he?_ Asmodai asks, Peter’s face smiling up at him. _One of your new protégés, Thomas how indelicate._ Thomas himself is past words already, panting harshly around the thin tendril of the demon, pressing down against his tongue. Thomas should know better, but he closes his eyes against the image, the demon pressing up against his mind with Peter’s face, pulling the image of a grumpy Peter, soaked to the bone and white shirt clinging under that ridiculous rain cloud to the surface. 

 _Oh, I will be eager for his visit._ Asmodai says. Thomas shakes his head to distraction, some variant of _don’t hurt him_ forming in the back of his mind as the demon works him over into his own release. Nightingale hopes vainly that Peter isn’t going to try the door. 

 

With how flimsy that thread of hope was, Thomas stares at the open door to the basement with a foreboding like prophecy. The darkness beyond the door gapes back at him, impenetrable. Thomas supposes he can only hope that Peter had completed his work before he grew distracted. The truth is, Thomas could turn and walk back to his own bedroom. He could engage the wards that will lock him in and wait respectfully until Peter has returned to his own room, or perhaps the tech cave, before re-emerging and saving them both the embarrassment. Thomas is feet from the door and already his mind’s eye is painted with what he might see if he just stepped forward and descended into the demon’s lair. He’s half hard in his trousers and his legs tremble as if pulled on by a swift tide. Thomas is afraid if he raises his foot to go, he’ll find himself pulled forward instead. His hand catches the wood of the doorframe, hot and not nearly as grounding as he might like under his fingers. Electricity stands every up hair along Thomas’s arms. His whole body prickles.

 

 _But you do want to see, don’t you?_ The demon asks. Thomas swallows and falls forward. The first few steps are a stumble, but Thomas catches himself, the door swinging gently closed behind him. Thomas will just retrieve Peter and they’ll both be thoroughly embarrassed as they leave but they’ll return to the case and refuse to speak of it again. Only, as the darkness parts, Thomas is able to see Peter suspended in the air before him. The demon smiles widely at Thomas and beckons him closer, a finger held to its lips. Thomas advances quietly, the room harsh around him with Peter’s keening breath. Peter’s eyes are unfocused, skin bared to the glorious ripple of muscle across his stomach, the firm jut of his prick where the demon wraps around him. Thomas can’t see what Peter is seeing. Some part of his mind ponders whether the Peter in front of him might just be another illusion, drafted for his own mind. 

 

Thomas feels the pluck of the demon at his own shirt and abandons his cufflinks carelessly. The plink, plink as they hit the floor doesn’t distract Peter, as wrapped as he clearly is in his own pleasure. Thomas blinks, trying to clear his mind, to remember his intention, but it’s a bit hard with one of Asmodai’s many tactile limbs worming down into his own trousers. Thomas doesn’t protest as he’s lifted from the floor, held in a familiar and friendly embrace. 

 _I believe this is something we’ve both wanted to see,_ Asmodai says, probing at Peter’s lips, Peter parts them on a groan, “Please, Sir.” clear enough for Nightingale to hear before the demon fills his mouth beyond words. Nightingale goes hot all over, and is grateful that the demon has managed to divest him of his clothing otherwise the rush of arousal might have neared painful. 

 _Do you want to know what he’s seeing?_ Asmodai asks Thomas. 

“No.” Nightingale whispers, though that’s not, strictly speaking, true. Thomas is afraid of what Peter might be seeing, afraid and desperately hopeful. It is better not to know. 

 _Well_ says the demon, _shall we put you to use?_ Nightingale is limp and unresisting as the demon carries him closer to Peter. From their relative positioning, it’s fairly clear what the demon is intending. Nightingale’s mouth is slick with anticipation, his mind unable to form a proper, cogent objection. 

 

Peter’s cock juts stiffly forward and he whines and bucks his hips as the demon’s tendril draws away. The demon slides Thomas forward, its appendages circling his wrists, pressing between his legs, and wrapping firmly around his back. Thomas’ lips part on a gasp and he’s close enough now for Peter to bump against him. Not quite aligned, Thomas turns his cheek, sloppily pressing his tongue against the head of Peter’s dick. Peter keens again. The demon’s appendage withdraws from Peter’s mouth long enough for him to gasp.

“God, that feels so real. You’ve never done two of him before.” Nightingale shudders as the demon chuckles, the sound rippling through his many limbs and vibrating everywhere they touch Nightingale’s body. 

 _I do my best for my favorite magicians._ The demon purrs. Thomas sucks insistently, bobbing his head the little he can, held still as he is by the demon. He can’t pull back far enough to let Peter fall from his lips and already Thomas is wishing he’d said something, anything at his entrance to this scene so that Peter might know. The feeling curls sickly in his stomach, realization zipping adrenaline down his spine, as the demon spreads his legs wider. 

 _There, there, Thomas. I never do anything that’s unwanted._ The demon murmurs. A hand grabs for Nightingale’s hair. It’s too real, defined fingers and a tight, shiveringly good grip. Thomas flicks his eyes up to Peter, and Peter is staring at him, rapt. 

“There are,” Peter’s breath hitches and his hips twitch in the demons hold, “demon-tentacle things around you too.” Despite the situation, Nightingale knows this tone, the observational cop-instinct voice that puts together clues. “The other Nightingale wasn’t being held.” Peter murmurs and Thomas can’t hold back the moan that image illicits. He’s hazy whether the image in his minds eye, Peter’s lips wrapped around his cock, is conjured by his own mind, or the demon. The hand in his hair wrenches, pulling tears into Nightingale’s eyes and Peter’s cock from his lips. The demon lets Peter haul him away. Thomas is sure the shine of spit on his lips and Peter’s prick is damning evidence enough. 

“Sir?” Peter says, clearly concerned. Thomas meets his eyes and fails to find anger. “Sir, are you alright?” 

Nightingale coughs. “I made a poor choice to enter, but it was of my own volition. I sincerely apologize for letting the situation and the demon’s pull get the better of me.” Thomas greatly wishes he could be having this conversation safely on an upstairs floor, and certainly someplace he wasn’t naked and extremely aroused. “I cannot possibly rectify this breach of trust and I-“ The demon tentacle that had been until now nestling, quiescent beneath him takes this moment to strike forward in a firm breach of Thomas’s sphincter, ending his sentence into a startled gasp. He is completely unable to stop the involuntary twitch of his own member or the tremor that runs over his body. Thomas clenches his fists and closes his eyes. The fact that Peter is watching makes it at once infinitely worse, and wholly too much better. Nightingale imagines he might feel Peter’s eyes like the sun on his skin, heating him to the core. When he manages to draw a shaky breath and return his attention to Peter’s face, Peter is staring at him gob smacked. 

 

“He’s really here.” Peter says to the demon, as if in confirmation. The demon’s agreement is laced with a smug pleasure Thomas takes abridgment to. “How did you ever lure him down here?”

 _You’re certainly the most effective leverage I’ve ever had,_ Asmodai says. _Normally he’s quite stubborn and elusive, more so than you have ever been_. Peter continues staring at Thomas. 

“Me?” he asks, his voice a sliver of it’s normal strength.

I _do strive to give my supplicants what they want. Thomas here is not particularly good at wanting things, and I thought your congruency would be so satisfying._ Asmodai sighs, closer to any sound of pleasure than Thomas has ever heard before. The tentacle within him twists and Thomas arches, failing to catch a whimper behind his teeth. Thomas draws a breath, steadying himself. 

“Peter-“ he begins, at the moment Peter blurts, “God, look at him.” and Asmodai purrs back his appreciation, the sound vibrating up inside of Thomas. Thomas clenches, gritting his teeth and catches Peter’s stare. 

“Peter, do you- are you comfortable with-”

“Like the demon says, nothing I don’t want,” Peter says. His hands stretch out toward Nightingale, but his fingers pause just above the skin of Thomas’ chest. Thomas can feel their warmth. 

“Do you want?” Peter checks.

“Yes.” Nightingale growls and the tentacle writhes over his back, carrying him forward until Peter’s fingers can dig into his shoulders and Peter’s mouth can meet his own. 

 

Peter makes a gratifyingly deep groan as his lips slide over Thomas’. Thomas catches Peter’s bottom lip with his teeth and Peter jerks against him delightfully. No sooner has Nightingale wished his own hands were free so he can run them over every inch of Peter before him than the demon slides away, bracing him by the shoulders and urging him closer to Peter. The brush of skin against skin is intoxicating. Thomas curls forward into Peter. Helpfully, Peter has arched his neck back, gorgeous little sounds falling from his lips as Thomas traces the taut muscle with his mouth. He sucks hard enough to leave bruises that bloom darkly across the brown of Peter’s skin and cause Peter to pant and writhe beneath him. 

 

Thomas is distracted enough that at first he doesn’t register the demon shifting them until the demon pulls him back, whispering, _Just_ look _at him,_ in Nightingale’s ear. Peter lays back, panting beneath him and Thomas runs appreciative fingers up his sides and over his chest. 

 _What do you think, Peter?_ Asmodai asks. 

“Oh, yes please.” Peter pants, his eyes catch hotly, hopefully on Nightingale’s. “Sir, may I-?” his hips give a slight involuntary jerk and with a shock of heat, Nightingale realizes what precisely the demon has positioned them for. Nightingale restrains the urge to grind down, all in good time.

“It’s Thomas,” he corrects instead, because if they’re going to do this…

“Thomas,” Peter breathes, like a punch to the gut. 

“Yes,” Thomas agrees, “Please.” Asmodai doesn’t need anymore than that, raising Peter’s hips up, holding Thomas open for him. Peter’s hands settle over Thomas’ hips holding him with a bruising grasp. The feeling is exquisite. Thomas has very little reference to compare it to, but the sensation is wholly separate from the twisting pleasure of one of the demon’s tentacles and the glory of being able to watch Peter’s face, his true face and not any illusion, more than steals his breath. Peter’s hips set up a quick, snapping rhythm as curses and praise fall from his lips in equal measure. Thomas stretches forward and feels the demon shift to his request till he can press himself against Peter, their lips tumbling together around gasped words. It isn’t quite a kiss, but Thomas relishes the closeness. His prick jerks against Peter’s abs, pressed between them. Peter’s fingers dig into the top of Nightingale’s arse and Nightingale tugs at Peter’s ear with his teeth in response. Asmodai seems to be delighted with the cacophony of sound they’re producing together. It’s probably the demon’s influence that’s managed to make the encounter this prolonged but there’s no impeding the climax Thomas is speeding for. 

 

The subtle wriggle of a tentacle working between them, wrapping tightly and surely around his erection with years of experience does Thomas in. His body convulses around Peter. Peter’s fingers squeeze sharply, his hips jerking unsteadily through a few last, sharp thrusts. The feeling of Peter’s prick sliding out is disquietingly wet, a new and unusual sound. Thomas holds Peter closer, arms wrapped comfortably around him. He’s relaxed enough that he startles only a little when one of the demon’s appendages wriggles up inside him again. It’s not precisely comfortable, shifting and flexing as it is, pressing against the spot that runs sparks over his spent nerves. Peter hums curiously and glances over Nightingale’s shoulder to see what’s happening. 

“I’ve noticed that it does that, collects semen. Do you think it has something to do with the absorption of energy? If it ran strictly on desire and lust, the physical byproduct shouldn’t be as important as the mind’s state. You’d think, if it’s really about driving you mad it’s the process of getting off rather than the outcome that matters? Or perhaps I’m missing something.” 

 _You could always try it again and take notes._ The demon suggests, reasonably. _I support experimentation._

“Peter.” Thomas sighs, resigned. He’s already quite familiar with the expression on Peter’s face. For once, he doesn’t feel any particular need to redirect Peter’s focus. This is one distraction that Thomas has to admit, he wouldn’t object to considering with science. At least, not if it means it’s likely to happen again, and soon. Nightingale frowns. “You do realize, Peter, that in order to complete a fully informed study you’ll have to consider the variables. It may be worth testing without exterior supernatural influence,” Nightingale hazards. It’s a fairly thin excuse but even for science Peter has his limits and Thomas can always claim he was suggesting it for empirical reasons and not any personal investment if Peter seems hesitant and they’re forced to salvage the situation. Peter smiles delightedly. 

“Definitely,” he says. He squeezes Nightingale’s hand and their fingers tangle together. It’s strange for such an innocent gesture to make Thomas’ pulse pound, not when they’re completely nude and being held up by a lust demon from the nth circle of hell. But Peter’s happy smile and his warm sure grip do that to a person’s heartbeat. 

Nightingale takes a breath, “For the moment though, it is likely in our best interest to head upstairs, separately. There’s the case,” Thomas blinks. “Did you manage to finish your reading before you were distracted?” 

“Oh!” Peter shakes his head, “I found something actually,” he begins as the demon reluctantly lowers his feet to the floor. Peter quickly grabs up his clothes and begins re-dressing. “I was actually about to leave to come find you.” He hops on one foot, adjusting his sock, “I didn’t get through all the books, but I think you’re going to like this.” Thomas leaves his socks off but puts his shirt back on. Peter is too distracted by his potential discovery to bother with a shirt, instead striding towards the door. Nightingale gives one moment to look back. The demon grins at him tentacles waving in an almost cheeky salute. Nightingale nods in return, then firmly closes the door behind them. He turns his attention fully back to Peter. 

“Alright, put your shirt on, we’ll take the Jag.” Halfway down the hall, Peter’s fingers wrap around his hand. Thomas’s eyes automatically jerk to Peter’s face. 

“Come on,” Peter says, grin curling around his lips. He gives a tentative tug and increases his pace until Thomas has to jog to keep up. Then with a startled laugh, they’re running together for the car. It’s plainly ridiculous and Thomas is glad he took a moment to tuck into his shoes, however odd it feels to be wearing them without socks. They reach the car and with a breathless laugh Peter raps the bonnet. 

“Come on, Thomas, we’ve got a murderer to catch.” Thomas helplessly returns the smile, sliding into the driver’s seat and starting the jag’s rumbling purr. 

“That we do,” he agrees, pulling out of the Folly with Peter at his side.

**Works inspired by this one:**

  * [[Cover Art] for "I'll meet you at the old mouse hole" by Pi (Rhea)](https://archiveofourown.org/works/10482810) by [Hamstermoon](https://archiveofourown.org/users/Hamstermoon/pseuds/Hamstermoon)




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